Reproducing apparatus for an optical recording medium

ABSTRACT

A reproducing apparatus reproduces an information signal from a card type optical recording medium from which an information signal can be optically read out and on which an information signal is discretely recorded as a plurality of blocks each consisting of a plurality of track trains. The apparatus comprises a detector formed with a plurality of detecting elements arranged two-dimensionally. A light beam from a reproducing light source irradiates the entire area of the block as a recording unit. The detector detects light reflected from the optical card, and a extractor extracts a detection output of one of the track trains in the block on the basis of a detection output from the detector.

BACKGROUND OF THE INVENTIQN

1. Field of the Invention

The present invention relates to a reproducing apparatus of an opticalrecording medium for reproducing information from an optical recordingmedium such as an optical card.

2. Description of the Prior Art

For instance, as disclosed in Japanese laid open patent No. 60-69873,No. 61-48135 No. 61-50115, and the like, as a construction regarding thereproduction of an information signal from an optical card, there hasbeen known a construction such that a laser beam is radiated onto tracktrains and a pit image corresponding to one track train is enlarged andformed onto a line sensor comprising, for instance, a CCD (ChargeCoupled Device) in which a number of photo sensitive elements arearranged in a straight line. Information of one track train can besimultaneously reproduced by using the line sensor. The optical card isfed step by step at the rate of three or four steps to one track train.A signal is reproduced by scanning at each position.

On the other hand, in Japanese laid open patent No. 62-52730, there hasbeen disclosed a construcion such that information recorded on anoptical recording medium is reproduced by using an area image sensor inwhich a number of photo sensitive elements are arranged on atwo-dimensional plane. That is, a system for reading out information ona unit basis of a block consisting of a set of track trains is disclosedin such literature.

The foregoing reproducing apparatus using the line sensor has a drawbacksuch that it is difficult to reproduce at a high speed because of theloss due to the movement time of the optical card.

The high speed reproduction can be performed by the system using thearea image sensor. However, according to the above literature, there isa problem such that the apparatus can be applied only to the card havingthe good linearity of the track trains such as a read only card which isformed from a mask by printing. That is, nothing is shown with respectto solutions in the case where the track trains and the detectingelements of the area image sensor are nonparallel because of a zigzagmotion of the track trains due to mechanical vibration when recording byusing a laser beam or due to a lack of compatibility among theapparatuses. To solve such a problem, there is considered a method ofproviding rectilinear guide grooves for guiding the recording beam sothat parallel track trains are formed in order to prevent the zigzagmotion of the track trains upon recording and to keep the parallel statebetween the scanning direction by the detecting elements of the areasensor and the track trains. However, since not only the memory capacityof a recording medium decreases but also it is meaningless to providethe guide grooves if they meander, rigorous technical management isneeded to form the guide grooves.

OBJECTS AND SUMMARY OF THE INVENTION

It is, therefore, an object of the present invention to provide areproducing apparatus of an optical recording medium in which the highspeed reproduction can be executed and even in the case where thedirection of track trains and the direction of detecting elements of animage sensor are not parallel, a signal can be accurately reproduced.

According to the present invention, the above object is accomplished bya reproducing apparatus for an optical medium comprising: an opticalrecording medium on which an information signal is recorded asrectilinear track trains and a plurality of recording units eachconsisting of a predetermined number of track trains are discretelyrecorded; a light source for irradiating a light to a whole area of oneof said recording units; detecting means consisting of a plurality ofdetecting elements arranged two-dimensionally for detecting the lightfrom the optical recording medium by the light source; and extractingmeans for extracting a detection output of one of the track trains inthe recording unit onto which the light is radiated by the light sourceon the basis of an output signal of the detecting means.

A digital signal is recorded as rectilinear track trains on an opticalrecording medium such as an optical card. A plurality of recording units(referred to as blocks) each consisting of a predetermined number oftrack trains are recorded in a matrix form on the optical card. Areproducing optical system which is moved relative to the optical cardis provided.

A reproducing light from a reproducing light source is radiated onto theoptical card. The radiating range covers the range of one block. Animage of the light irradiated block is formed onto an area image sensorconsisting of a CCD through an enlarging lens. A multi gradation signalfrom the image sensor is read out and converted into a digital signaland, further, written into a memory. The reproduction data of each tracktrain is read out of the memory and the portions having no signal aredetected. The maximum value of the signal is detected in the regionbetween the non-signal portions. The maximum value is held into a linememory of one track train. The maximum value corresponds to the signalrecorded in the track train. The reproduction data is sequentially readout of the line memory. Even when the arranging direction of the imagesensor consisting of a CCD and the extending direction of the tracktrains do not completely coincide, the data of each track train can beread out.

In the invention, the high speed reproduction can be executed by thearea image sensor.

The above and other objects and features of the present invention willbecome apparent from the following detailed description and the appendedclaims with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing an optical card in an embodiment of thepresent invention;

FIG. 2 is a schematic diagram showing one block on the optical card;

FIG. 3 is a schematic diagram of a data arrangement of one track;

FIGS. 4A and 4B are a schematic diagram and a perspective view forexplaining a reproducing optical system;

FIG. 5 is a schematic diagram for explaining an image sensor;

FIG. 6 is a schematic diagram showing a pit image which is formed on theimage sensor;

FIG. 7 is a block diagram of an example of a reproducing circuit;

FIGS. 8 to 10 are block diagrams showing three examples of a non-signaldetecting circuit; and

FIGS. 11A and 11B are schematic diagrams for explaining the operation toreproduce a signal from a track train.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

An embodiment of the present invention will be described hereinbelowwith reference to the drawings in accordance with the following order.

a. Optical card

b. Reproducing optical system

c. Reproducing circuit

d. Non-signal detecting circuit

e. Reproduction of signal from track train

a. Optical Card

In FIG. 1, reference numeral 1 denotes an optical card in theembodiment. The optical card 1 is constructed by laminating a protectivesubstrate, a recording film, and a back layer serving as a protectivelayer of the recording film. The recording film is made of a materialsuch as antimony-selenium, bismuth-tellurium, or the like whosereflectance changes when it is irradiated by a laser beam. The opticalcard 1 is what is called a WORM type since an information signal can beoptically recorded. A digital information signal is recorded on theoptical card 1 on a unit basis of a block consisting of a plurality oftrack trains. However, the optical card 1 of the invention does not havea guide groove to rectilinearly guide a laser beam from a recordinglight source of a recording optical system when an information signal isrecorded (a guide groove a also be used to guide a laser beam from areproducing light source when the information signal is reproduced by areproducing optical system), a prepattern which is used for making thescanning direction by the detecting means and the track trains parallel,and or the like. For instance, sixteen stripes each consisting of 100blocks are formed on the optical card 1. As shown in FIG. 2, one blockcomprises 120 tracks and data of 20 bytes is recorded as an opticalpattern in one track train.

In the recording mode, the optical card 1 is fed step by step at apredetermined pitch in a y direction in FIGS. 1 and 2 by card feedingmeans. By scanning the recording film in an x direction by a recordinglaser beam, each track train is formed. The scanning of the laser beamis executed by beam scanning means such as a galvano mirror or the likeprovided for the recording optical system. In the reproducing mode, whena predetermined block is accessed, data of one block is reproduced in astate in which both the optical card 1 and the reproducing opticalsystem are at rest. To access a predetermined block, the optical card 1is fed in the y direction at a predetermined interval, for instance, ona block unit basis by the card feeding means and the reproducing opticalsystem is moved in the x direction by the optical system feeding means,thereby enabling a predetermined block to be accessed.

A predetermined block can be also accessed by fixing either one of thereproducing optical system and the optical card and by moving the otherin the x and y directions.

On the other hand, the recording data of one track train has such aconstruction as shown in FIG. 3. A preamble of two bytes is added in thebeginning. A sync signal of two bytes is then added. Data of 12 bytes islocated after the sync signal. Check data of four bytes (redundancy codeof error correction code) is added after the data. For instance, aproduct code which is completed in one block is used as the errorcorrection code.

b. Reproducing Optical System

FIGS. 4A and 4B show an example of the reproducing optical system. Theoptical card 1 is formed by laminating a protective substrate 2, arecording film 3, and a back layer 4 also functioning to protect boththe protective substrate 2 and recording film 3. A display section isformed on the surface of the back layer 4 as necessary by printing orthe like. As shown in FIG. 4B, the optical card 1 is fed in the ydirection by a driving roller 5 of the card feeding means. Although notshown, the driving roller 5 is rotated by a stepping motor in therecording mode and is rotated by a DC motor in the reproducing mode.

The reproducing optical system has a reproducing light source, forinstance, a light emitting diode 6. The reproducing light emitted fromthe light emitting diode 6 is converted into the parallel light by acondenser lens 7 and is transmitted to a half mirror 8 to bend theoptical path of the parallel reproduction light by 90°. The parallellight is bent by 90° by the half mirror 8 and is radiated onto theoptical card 1 through an image forming lens 9. An irradiating range ofthe reproducing light is set to a range of one block. In the embodiment,to access a predetermined block, the optical card 1 is fed in the ydirection on a block unit basis and the reproducing optical system canbe moved in the x direction. In this case, as mentioned above, it isalso possible to construct the apparatus so that the optical system isat rest and the optical card 1 is moved in the x and y directions by anx-y stage.

The reflected light of the reproducing light is projected through thehalf mirror 8 and a mirror 10 onto an area image sensor 11 comprising aCCD or the like on which picture elements are two-dimensionallyarranged. The optical image of one block is formed onto the area imagesensor 11. In the track trains on the recording medium, the datarecording portion irradiated by the laser beam from the recordingoptical system and the portion not thus irradiated have an opticaldensity difference, that is, different reflectances. As shown in FIG. 5,the area image sensor 11 has 480 picture elements in the feedingdirection (y direction) of the optical card 1 and has 640 pictureelements in the direction (x direction) of the track trains.

The reproducing optical system is constructed as an enlarging opticalsystem. The image of one block is enlarged, for instance, four times andformed onto the image sensor 11. For instance, as shown in FIG. 6, theimage of the minimum pit having a diameter of 5 μm is formed onto fourpicture elements having the size of picture element of (10 μm×10 μm) ofthe image sensor 11. When a track pitch is set to 10 μm, the image ofone block consisting of 120 track trains is formed onto the image sensor11 of (480×640 elements). Assuming the shortest recording wavelength isset to 10 μm/pitch, data of 20 bytes is enclosed in one track. The 20bytes have the data arrangement shown in FIG. 3. As will be obvious fromFIG. 3, since data of 12 bytes is included in one track, data of (120×12=1.44 kbytes) can be recorded in one block.

The image sensor 11 has a construction similar to that of the sensorused in a video camera. The signal charges are sequentially read out inthe direction of the track train and the whole signal of the imagesensor 11 is completely read out for a time of (1/60) second. Therefore,the image signal can be read out at a high speed of 86.4 kbytes/sec(=60×1.44 kbytes).

c. Reproducing Circuit

The multi gradation output signal from the image sensor 11 is suppliedto an A/D converter 20 as shown in FIG. 7. A drive clock which issupplied from a clock generating circuit 21 to the image sensor 11 isalso supplied to the A/D converter 20. The output signal of each pixelof the image sensor 11 is converted into the digital signal of eightbits. The digital signal from the A/D converter 20 is written into a RAM22.

The RAM 22 has addresses in the x and y directions which correspond tothe positions of the picture elements of the image sensor 11 in aone-to-one correspondence relation. The output signal of each pictureelement is written into the corresponding address. The address in the ydirection is formed by an address generating circuit 23. The address inthe x direction is formed by an address generating circuit 24. Both ofthe addresses in the x and y directions are supplied to the RAM 22. Acontrol signal to control the writing and reading operations for the RAM22 is supplied from a control circuit 25.

When the output signal of the image sensor 11 is written into the RAM22, the reading operation of the RAM 22 is started. The digital signalsof the track trains extending in the x direction (lengthwise directionof the track trains) are successively read out of the RAM 22. Thereadout output of the RAM 22 is supplied to a non-signal detectingcircuit 26 and is also supplied to one input terminal of a digitalcomparator 28 through a delay circuit 27. The delay circuit 27 isprovided to delay the data by a time which is required to detect anon-signal. An output signal of an RAM 31 is supplied to the digitalcomparator 28. The digital comparator 28 compares the data of eight bitsread out of the RAM 22 with the data of eight bits read out of the RAM31 and outputs the data having a larger value.

The output data of the digital comparator 28 is supplied to one inputterminal of a selector 29. Zero data is supplied from a terminal 30 tothe other input terminal of the selector 29. Output data of the selector29 is input to the RAM 31. When the non-signal is detected, the zerodata is selectively supplied to the RAM 31 by the selector 29 and theRAM 31 is cleared.

The RAM 31 is a line memory which can store data of one train of theimage sensor 11 or RAM 22. The address in the x direction is suppliedfrom the address generating circuit 24 to the RAM 31. On the other hand,the control signal to control the writing and reading operations is alsosupplied from the control circuit 25 to the RAM 31. As will be explainedhereinlater, the maximum value of the data which is obtained for aperiod of time from the detection of the train of the non-signal to thedetection of the next train of the non-signal is stored into the RAM 31.

The maximum value of the data is read out of the RAM 31 and supplied toa binarizing circuit 33 through a gate circuit 32. The gate circuit 32is controlled by a control signal from the control circuit 25. Only thedata of the maximum value stored in the RAM 31 is supplied to thebinarizing circuit 33. The maximum value data is converted into thebinary data by the binarizing circuit 33 and the binary data is suppliedto a reproducing processor 34. The reproducing processor 34 has acircuit to perform the demodulation of the digital modulation, forinstance, phase coding, an error correction circuit, and the like andexecutes an error correcting process on a block unit basis. Thereproduction data is taken out to an output terminal 35 of thereproducing processor 34.

d. Non-signal Detecting Circuit

The non-signal detecting circuit 26 detects a non-signal region betweentrack trains. FIG. 8 shows an example of the non-signal detectingcircuit 26. In FIG. 8, the data read out of the RAM 22 is supplied to aninput terminal 41. A threshold value is supplied to an input terminal42. The difference (=the output of the RAM 22-the threshold value)between the input signals is calculated by a subtracting circuit 43. Abit in which the most significant bit of the difference is inverted isoutput from the subtracting circuit 43 and supplied to an AND gate 44.The output bit of the subtracting circuit 43 is set to the high levelwhen the difference has a positive value, that is, when the output ofthe RAM 22 is larger than the threshold value.

A clock pulse is supplied from a terminal 45 to the AND gate 44. Theclock pulse transmitted through the AND gate 44 is supplied as a clockto a counter 46. The counter 46 is cleared by a clear pulse from aterminal 47 each time the data of one train is read out of the RAM 22. Acount value of the counter 46 is supplied to a comparator 48 andcompared with a threshold value from a terminal 49. For instance, whenthe count value of the counter 46 is smaller than the threshold value,the comparator 48 generates a detection signal of the high level.

As mentioned above, when the data read out of the RAM 22 is larger thanthe threshold value, the output signal of the subtracting circuit 43 isset to the high level and the clock pulse is supplied through the ANDgate 44 to the counter 46. Therefore, when the data of one train is readout of the RAM 22 and when a signal exists, the count value of thecounter 46 has a large value and the output signal of the comparator 48is set to the low level. On the other hand, when no signal exists in onetrain read out, the count value of the counter 46 has a small value andthe output signal of the comparator 48 is set to the high level.Reference numeral 50 denotes an output terminal.

FIG. 9 shows another example of the non-signal detecting circuit 26. Anoutput of an adder 51 and the readout data of the RAM 22 which is inputfrom a terminal 52 are added by the adder 51. The adder 51 is reset by areset signal from a terminal 53 each time the data of one train is readout. The output signal of the adder 51 is supplied to a comparator 54and compared with a threshold value from a terminal 55. When theaddition output of the adder 51 is smaller than the threshold value, thecomparator 54 generates a detection signal of the high level to anoutput terminal 56.

When a signal exists in the data of one train which was read out of theRAM 22, the addition output of the adder 51 has a large value and thedetection signal obtained at the output terminal 56 is set to the lowlevel. On the other hand, when no signal exists in the data of one trainwhich was read out of the RAM 22, the addition output of the adder 51has a small value and the detection signal obtained at the outputterminal 56 is set to the high level.

Further, a non-signal can be also detected at the stage of an analogsignal. As shown in FIG. 10, an analog output signal from the imagesensor 11 is supplied to a terminal 57. The analog output signal and areference voltage formed by a variable resistor 59 are compared by alevel comparator 58. When the level of the analog output signal issmaller than the reference voltage, the level comparator 58 generates ahigh level detection signal. The high level detection signal is takenout to an output terminal 60.

e. Reproduction of Signal from Track Train

It is ideal that the track trains formed on the optical card 1 and thearrangement in the x direction of the picture elements of the CCD imagesensor 11 are parallel. However, the track trains and the arrangement inthe x direction of the picture elements of the image sensor 11 are notalways parallel in the case where there are positional differences amongthe optical card 1, the recording optical system, and the reproducingoptical system, where the optical card recorded by another apparatus isreproduced, or the like. Even in this case, it is necessary that aninformation signal can be accurately reproduced from the track train.

FIG. 11A shows the ideal case where track trains T_(i), T_(i+1), andT_(i+2) on the optical card 1 and the arrangement in the x direction ofthe picture elements of the image sensor 11 are parallel. In FIG. 11A,an amount of data of one track is shown shorter than the actual amountfor representation and explanation. Each of the output signals of thepicture elements of the image sensor 11 is converted into the digitalsignal by the A/D converter 20 and written into the address in the RAM22 which corresponds to one of the picture elements in a one-to-onecorresponding relation.

The output signals of track trains n, n+1, n+2, . . . of the imagesensor 11 in FIG. 11A are sequentially read out and converted into thedigital signals by the A/D converter 20 and written into the RAM 22. Thedigital signal of each train is read out of the RAM 22. When the data ofthe train n is first read out, the detection signal is generated fromthe non-signal detecting circuit 26 since the train n is the non-signaltrain. The detection signal is supplied to the control circuit 25. Theselector 29 selects the zero data by the control signal generated fromthe control circuit 25. On the other hand, in the RAM 31 as the linememory, the writing and reading operations are time-sharingly executedand, further, the gate circuit 32 is turned on. That is, the previousmaximum value stored in the RAM 31 is read out and the zero data iswritten into the RAM 31 through the selector 29 and the RAM 31 iscleared. The readout data of the RAM 31 is supplied to the binarizingcircuit 33 through the gate circuit 32.

In the next train n+1, the above operations are repeated since the trainn+1 is similarly a non-signal train. However, the gate circuit 32 is notturned on and the data of the non-signal train is not supplied to thebinarizing circuit 32.

Since the train n+2 is not a non-signal train, the selector 29 selectsthe output data of the digital comparator 28. The output data of thedigital comparator 28 is written into the RAM 31. The data of the trainn+2 is written into the RAM 31. The data of the train n+3 is alsowritten into the RAM 31. The data having a higher level between the dataof the trains n+2 and n+3 is output from the digital comparator 28 andwritten into the RAM 31. Since the next train n+4 is detected as anon-signal train, the data of the maximum value stored in the RAM 31 issupplied through the gate circuit 32 to the binarizing circuit 33 andthe RAM 31 is cleared. In the binarizing circuit 33 or reproducingprocessor 34, only the maximum value data from the RAM 31 is used aseffective data.

Different from the case of FIG. 11A, actually, as shown in FIG. 11B, inmany cases, the lengthwise directions of the tracks T_(i), T_(i+1),T_(i+2), . . . and the arrangement in the x direction of the pictureelements of the image sensor 11 are not parallel. Even in this case, themaximum value data is stored into the RAM 31 in a manner similar to theforegoing operation.

In the example of FIG. 11B, the train n is detected as a non-signaltrain and the maximum value among the output signals of the trains n+1,n+2, and n+3 located in the region between the train n and the nextnon-signal train n+4 is stored into the RAM 31. The maximum value issupplied as a reproduction signal of the track T_(i+1) to the binarizingcircuit 33 through the gate circuit 32.

The present invention is not limited to the WORM type optical card butcan be applied to the recording and reproduction of information onto andfrom other optical recording media such as a ROM type optical card,erasable type optical card, and the like.

According to the invention, a signal can be read out from an opticalrecording medium and the high speed reproduction can be executed withoutchanging the relative positional relation between the optical system andthe optical recording medium. On the other hand, according to theinvention, even in the case where the directions of the track trains andthe the detecting elements of the area image sensor are not parallel,the signal can be accurately reproduced.

We claim:
 1. A reproducing apparatus comprising:an optical recordingmedium from which an information signal can be optically read and ontowhich an information signal is discretely recorded as a plurality ofrecording units each comprising a plurality of track trains; a lightsource; an optical system for causing a light beam from said lightsource to irradiate a whole area of one of said plurality of recordingunits and for guiding a light beam reflected from said recording medium;detecting means comprising a plurality of detecting elements arrangedtwo-dimensionally for detecting said reflected beam as guided by saidoptical system; extracting means for extracting a detection output ofone track train of said recording unit irradiated by said light sourceon the basis of an output signal of the detecting means and including acomparing means for successively comparing the detection outputs fromsaid detecting means and a line memory means for storing an output ofsaid comparing means; and memory means for storing digitally converteddetection output from said detecting means and including a first addressgenerating circuit to generate an address in a direction parallel withsaid track trains and a second address generating circuit to generate anaddress in a direction perpendicular to the said track trains, and inwhich an address signal from said first address generating circuit isalso supplied to said line memory means.
 2. An apparatus according toclaim 1, wherein said extracting means has non-signal recording portiondetecting means for detecting non-signal recording portions among thetrack trains in said recording unit.
 3. An apparatus according to claim2, wherein as the detection signal of one track train in the recordingunit, said extracting means outputs the maximum one of output signals ofthe detecting elements of said detecting means which are obtained for aperiod of time from the detection of the non-signal recording portion bysaid non-signal recording portion detecting means to the detection ofthe next non-signal recording portion.
 4. An apparatus according toclaim 3, further comprising gate means for supplying the output signalfrom said extracting means to a reproduction processor when saidnon-signal recording portion detecting means detects the next non-signalrecording portion.
 5. An apparatus according to claim 4, whereinsaidcomparing means successively compares the detection outputs whichare output from said detecting means for a period of time until the nextnon-signal recording portion is detected by said non-signal recordingportion detecting means and produces as an output the larger detectionoutput.
 6. An apparatus according to claim 5, wherein said extractingmeans has control means for allowing the comparison output signal ofsaid comparing means and a clear signal to be selectively supplied tosaid line memory means when the next non-signal recording portion isdetected by said non-signal recording portion detecting means.
 7. Anapparatus according to claim 5, wherein said comparing means comprises adigital comparator to compare output signals from said memory means. 8.An apparatus according to claim 2, wherein said non-signal recordingportion detecting means comprises a counter and a comparator forcomparing an output signal from said counter with a threshold value, andwhen the output signal from said detecting means has a value equal to orexceeding a predetermined value and the output signal of said counter issmaller than said threshold value, said detecting means outputs anon-signal detection output.
 9. An apparatus according to claim 2,wherein said non-signal recording portion detecting means comprises anadder for adding a detection output from said detecting means and acomparator for comparing an output signal of said adder with a thresholdvalue, and when the output signal of said adder is smaller than saidthreshold value, said detecting means outputs a non-signal detectionoutput.
 10. An apparatus according to claim 2, wherein said non-signalrecording portion detecting means has a comparator for comparing adetection output from said detecting means with a threshold value, andwhen the detection output from said detecting means is smaller than saidthreshold value, said detecting means outputs a non-signal detectionoutput.
 11. A reproducing apparatus for reproducing an informationsignal discretely recorded on an optical recording medium as a pluralityof recording units each comprising a plurality of track trains, saidapparatus comprising:a light source; an optical system for causing alight beam from said light source to irradiate a whole area of one ofsaid plurality of recording units and for guiding a light beam reflectedfrom said recording medium; detecting means comprising a plurality ofdetecting elements arranged two-dimensionally for detecting saidreflected beam as guided by said optical system; extracting means forextracting a detection output of one track train of said recording unitirradiated by said light source on the basis of an output signal of thedetecting means, including comparing means for successively comparingdetection outputs from said detecting means and line memory means forstoring an output of said comparing means; and memory means for storingdigitally converted detection output from said detecting means andincluding a first address generator for generating an address in a firstdirection parallel to said track trains and a second address generatorfor generating an address in a direction perpendicular to said tracktrains, and in which an address signal from said first address generatoris fed to said line memory means.